This invention relates to a method and an apparatus for spreading granular material, especially a fertilizer.
The invention is especially intended for use in connection with fertilization of rock banks, road slopes and cuttings and other hardly accessible areas which cannot be reached by conventional spreading apparatus.
In conventional spreaders the fertilizer is dosed continuously to centrifugal blades, pendulum tubes and the like, which accelerate the material to a higher velocity. However, these spreaders have a very limited spreading range and they are generally intended for fertilizing easily accessible areas, such as an agricultural area.
There is also known a spreading apparatus in which the fertilizer is accelerated and transported by feeding into a continuous air stream, e.g. from a fan or a compressor. The fertilizer then aquires a spreading velocity which at best almost corresponds to the velocity of the air stream. By these means is obtained a spreading range which is wider than that of the abovementioned conventional spreaders. However, in most cases none of these air based spreading devices have a sufficient range to cover in a satisfactory manner such hardly accessible areas as mentioned above. Further, it is often desireable in such cases to be able place the fertilizer onto selected areas of relatively limited extent, which is hardly possible with most of the known mechanical types of spreaders.